Room-temperature transparent oxide spin electronics: A conducting interface in $\mathrm{LaFe}{\mathrm{O}}_{3}\ensuremath{-}\mathrm{SrTi}{\mathrm{O}}_{3}$

Letter

Room-temperature transparent oxide spin electronics: A conducting interface in $LaFe O_{3} - SrTi O_{3}$

Ripudaman Kaur, Anamika Kumari, Shinjini Paul, Mohd Anas, Bibek Ranjan Satapathy, Sanjeev Kumar, V. K. Malik, P. Mahadevan, D. D. Sarma, and Suvankar Chakraverty

Phys. Rev. B 109, L201114 – Published 14 May 2024

Abstract

The quest for realizing highly spin-polarized conduction in materials at room temperature is one of the central themes of materials physics. We report on the realization of a conducting interface in $LaFe O_{3}$ (LFO)- $SrTi O_{3}$ (STO) that demonstrates spin-polarization signatures, namely, negative magnetoresistance (MR) and anomalous Hall resistivity $> 150$ K and even up to room temperature. However, the same system shows positive MR and normal Hall effect at temperatures $< 150$ K. From density functional theory calculations, we find that this is related to the structural transition of the substrate, amplified here as the changes happen at the interface. This leads to a net spin polarization of the interface states at the Fermi energy in the high-temperature phase, allowing for an anomalous Hall effect and negative MR. In addition, this interface appears to be almost transparent in the entire range of visible light. Our observation might be viewed as a step toward room-temperature transparent oxide spintronics.

Received 10 January 2023
Revised 4 January 2024
Accepted 14 March 2024

DOI:https://doi.org/10.1103/PhysRevB.109.L201114

Physics Subject Headings (PhySH)

Electrical conductivity Magnetotransport

2-dimensional systems Interfaces Perovskites Thin films

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ripudaman Kaur^1,2,*, Anamika Kumari^1,*, Shinjini Paul³, Mohd Anas⁴, Bibek Ranjan Satapathy¹, Sanjeev Kumar², V. K. Malik⁴, P. Mahadevan³, D. D. Sarma^5,6, and Suvankar Chakraverty ^1,†

¹Quantum Materials and Devices Unit, Institute of Nano Science and Technology, Mohali, Punjab 140306, India
²Applied Science Department, Punjab Engineering College (Deemed to be University), Sector-12, Chandigarh 160012, India
³S. N. Bose National Centre for Basic Sciences, Kolkata, West Bengal 700106, India
⁴Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, India
⁵CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Industrial Estate P.O., Pappanamcode, Thiruvananthapuram 695019, India
⁶Solid State and Structural Chemistry Unit, Indian Institute of Science Bengaluru, Karnataka 560012, India

^*These authors contributed equally to this work.
^†suvankar.chakraverty@gmail.com

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Vol. 109, Iss. 20 — 15 May 2024

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Figure 1
Schematic and resistivity measurements. (a) Schematic of the LFO-STO heterostructure showing alternately charged layers arrangement in both LFO and STO that leads to the formation of the two-dimensional electron gas (2DEG) at the interface. (b) Temperature-dependent 2D resistivity of LFO-STO interface.
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Figure 2
Magnetotransport measurements at 300 and 100 K. (a) and (b) % magnetoresistance (right axis) and Hall resistance (left axis) as a function of the temperature of the LFO-STO interface measured at 100 and 300 K, respectively. (c) and (d) Raw Hall data (black) marked as $R_{x y}$ as a function of the applied magnetic field, the linear fit (red) of the raw data, and the subtracted part (blue) of the raw data from the linear fit marked as anomalous Hall resistance ( $R_{x y}^{AHE}$ ) for LFO-STO interface at 100 and 300 K, respectively.
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Figure 3
Temperature-dependent magnetotransport and superconducting quantum interference device (SQUID) measurements. (a) Magnetoresistance (MR) of the LFO-STO interface as a function of the applied magnetic field measured at selected temperatures as marked in the figure. (b) Anomalous Hall resistance of the LFO-STO interface as a function of the applied magnetic field measured at selected temperatures as marked in the figure. (c) Magnetization of LFO-STO (black) and annealed STO (red) as a function of temperature measured under the application of 100 Oe magnetic field. (d) % MR (left axis) and anomalous Hall resistance (right axis) as a function of the temperature of the 6 ml LFO-STO interface. (e) The density of states (DOS), for the interfacial Fe (in Navy line) and Ti (in red line) $d$ orbital, is plotted along with the spin-polarized DOS ( $m_{z}$ contribution of $d$ orbital) of the interfacial Ti (up in pink line and down in blue line) for both when the substrate is in low temperature (tetragonal phase) and in high temperature (cubic phase).
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Figure 4
Magnetotransport measurements for LFO-STO, LVO-STO, LAO-STO, and Nb-STO at 300 K and band schematic for LFO-STO interface. (a) % magnetoresistance (MR) as a function of the applied magnetic field measured at 300 K for conducting interface LFO-STO with different thicknesses of LFO thin films (4, 6, 10, and 40 ml) as mentioned in the figure. (b) Hall resistance as a function of the applied magnetic field measured at 300 K for conducting interface LFO-STO with different thicknesses of LFO thin films (4, 6, 10, and 40 ml) as mentioned in the figure. The inset presents the anomalous part of these samples as a function of the applied magnetic field. (c) % MR (left axis) and anomalous Hall resistance (right axis) as a function of charge carrier density (mentioned at the bottom axis) formed at the conducting interface of LFO-STO with different LFO thicknesses (mentioned at the top axis). (d) % MR as a function of the applied magnetic field measured at 300 K for conducting interface of LAO-STO, LVO-STO, LFO-STO, and Nb-doped single crystal of STO as mentioned in the figure. The inset shows the zoomed version of the same. (e) Anomalous Hall resistance as a function of the applied magnetic field measured at 300 K for conducting interface of LAO-STO, LVO-STO, LFO-STO, and Nb-doped single crystal of STO as mentioned in the figure. The inset shows the raw Hall data without linear subtraction. (f) % transmission of light as a function of light energy. The inset presents the real image of the sample.
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Physical Review B

covering condensed matter and materials physics

Room-temperature transparent oxide spin electronics: A conducting interface in $LaFe O_{3} - SrTi O_{3}$

Ripudaman Kaur, Anamika Kumari, Shinjini Paul, Mohd Anas, Bibek Ranjan Satapathy, Sanjeev Kumar, V. K. Malik, P. Mahadevan, D. D. Sarma, and Suvankar Chakraverty

Phys. Rev. B 109, L201114 – Published 14 May 2024

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Physical Review B

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Room-temperature transparent oxide spin electronics: A conducting interface in LaFeO3−SrTiO3

Ripudaman Kaur, Anamika Kumari, Shinjini Paul, Mohd Anas, Bibek Ranjan Satapathy, Sanjeev Kumar, V. K. Malik, P. Mahadevan, D. D. Sarma, and Suvankar Chakraverty

Phys. Rev. B 109, L201114 – Published 14 May 2024

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Room-temperature transparent oxide spin electronics: A conducting interface in $LaFe O_{3} - SrTi O_{3}$